Mercury relay



Jan. 29, 1946. u. c HEDIN 2,393,904

' unacumr RELAY Filed Dec. :50, 1939 2 Sheets-Sheet 1 INVENT OR.

ATTORNEY U. C. HEDIN MERCURY RELAY Jan. 29, 1946.

2 Sheets-Sheet 2 Filed Dec. 30, 1939 INVENTOR.

BY WM 5 MW ATTORNEY Patented Jan. 29, 1946 MERCURY RELAY Uno C. Hedln, Elkhart, Ind., assignor, by inesne assignments, to Herbert E. Bucklen, Jr., Elkhart, Ind.

Application December 30, 1939, Serial No. 311,915

8 Claims.

This invention relates to mercury relays, and more particularly is directed to mercury relays of the displacer type comprising a metallic envelope having two electrodes spaced apart by meansof a ceramic or refractory member with bodies of mercury retained in contact with one or both of the electrodes and adapted to provide bridging contact between the electrodes for completing a circuit upon displacement of a plunger or the likethrough magnetic action.

One of the primary objects of the present invention is to provide a metallic envelope mercury relay which will avoid the objections heretofore encountered in the use of glass relays in which the glass envelope was frequently cracked or broken during shipment or in use by reason of the action of the displacer, which must necessarily have a magnetic material associated therewith and which, when moved rapidly, might engage the glass envelope with sufilcient force to break the same. In fact, in such previous constructions using glass envelopes it became necessary to employ cushioning means for the ends of the displacer to insure against too rapid movement thereof or shifting thereof during shipping, which means, however, was not wholly effective.

Another object of the present invention is to provide a construction in which the mercury relay can be readily mounted in a solenoid or the like,

' and is capable of assuming various axial positions therein by use of a novel type of spacing and clamping means so that relays of various capacities may be employed with the same solenoid mounting bracket.

Still another feature of the present invention is to provide a mercury relay construction in which the major portion of the component parts are similar to or identical with portions of the metal envelope mercury switches of the type now on the market, and as disclosed in the Paul S. Bear patents, Nos. 2,132,921 and 2,132,922, issued October 11, 1938, respectively. This allows mass production of certain of the parts, insuring economy of manufacture and facilitating conversion of the switches into mercury relay switches of the displacer type without a great deal of tooling expense.

Another feature of the present invention is to provide mercury relays which may be of either the normally open or the normally closed type without greatly changing the internal construction of the switch.

Still another feature of the present invention is to provide an improved mounting for holding the switch in fixed axial non rotative position within the solenoid core.

Other objects and advantages of the present invention will be more apparent from the following detailed description which, taken in conjunction with the accompanying drawings,. will disclose to those skilled in the art the particular construction and operation of a preferred form of the present invention.

In the drawings:

Figure 1 is a sectional view through one form of mercury displacer embodying the present invention;

Figure 2 is an elevational view, partly in section, of a switch such as shown in Figure 1 in conjunction with the mounting bracket for the solenoid;

Figure 3 is a plan view of the structure shown .inFigure 2;

Figure 4 is a vertical sectional view through a mercury relay of the normally open type;

Figure 5 is a similar sectional view of a modified form of switch utilizing the tubular open ended envelope;

Figure 6 isa still further modified construction somewhat similar to that shown in Figure 1 but showing a switch of the normally closed type; and

Figure 7 is an elevational view, partly in section, showing a still further modified form of envelope structure.

Referring now in detail to the drawings, in Figure 1 I have shown a metallic envelope 5 having the enlarged end portion 6 joined to the main tubular body portion by the frusto-conical shoulder I. This envelope must be of the austenitic type, and may comprise stainless steel or a non-magnetic material that does not amalgamate with mercury. A stainless steel of the 18-8 group is preferable, having not less than 24% chromium and nickel combined, but not less than 8% of each element; The shell has an enlarged open end in which is inserted the ceramic or refractory member 8 having a frusto-conical shoulder portion 9 seating on the shoulder 1 and axially locating the refractory 8 in position. The shoulder 9, together with the inwardly extending cylindrical portion ill of reduced diameter, form means for radially centering the insert within the envelope.

The insert 8 is provided with the tubular extending portion l2, which is bored as indicated at H, to form an axial passage therethrough, opening out at its lower end through the flared portion [4 into the face l5 of an electrode head It secured in the counterbored lower end of the insert 8. The electrode head I8 is of an axial extent such as to fit fully within the end of the insert 8, and has the central projecting shank i1 projecting outwardly of the open end of the envelope 8. Seated against the rear face of the electrode head l8 and the lower end of the insert 8 is an elastic compressible sealing means l8. such as rubber or the like, forming a gasket having the projecting skirt or lip portion 18 extending about the frusto-conical shoulder formed on the insert 8. The gasket I8 is compressed in position by means of a refractory compression member 88 which extends into the open end of the envelope and has the reduced cylindrical portion 88 encircling the shank ll of the electrode outwardly of the envelope end. The entire assembly is maintained under compression to force the gasket l8 into sealing engagement with the internal walls of the envelope by means of the metallic retaining ring 28 held in position by the spunover edge 28 at the open end of the envelope. The retaining ring 28 is connected to one side of the circuit controlled by the relay through the conductor 28, electrically bonded thereto. The electrode shank i1 is connected to the opposite side of the circuit through the conductor 81 secured to the projecting end of the shank outwardly of the shouldered portion 22 of the compression member 28, and is preferably encased within a hard setting cementitious material. such as indicated at 28, which forms a water-proof bond over the terminal and the end of the compression member 28.

The envelope assembly is preferably enclosed within an insulated molded case formed of two pieces comprising the main body portion 88 which extends about the closed end of the envelope and is shouldered to enclose the enlarged end of the envelope, being notched as indicated at 88' for leading out the conductor 88. The end of the case member 88 is closed by a cup-shaped cap member 88 which is rabbeted into the end thereof and suitably cemented thereto.

Disposed within the tubular body of the envelope 8 and radially spaced from the extension I! of the insert 8 is a circular plunger 88 comprising an inner member of refractory insulating material 88 and an outer tubular shell 81 of magnetic material such as soft iron or the like. Adjacent opposite ends the cylindrical sleeve 88 is provided with radially extending circumferentially spaced projections 88 which extend through suitable apertures formed in the iron sleeve 81 to locate the iron sleeve against axial movement relative thereto, and also to provide insulating bumpers for preventing contact between the iron sleeve 81 and the metallic shell 8. Disposed in the bore i8 of the extension I! and lying in contact with-the face ii of the electrode is a body of mercury 88 which, at its upper end has the meniscus curve 82 lying within the circular edge of the sleeve i2. Disposed on the outside of the sleeve 12 and in the annular space between the external sleeve I! of the tubular portion 8 is a second body of mercury 88 in which the lower end of the displacer 88 is immersed. Due to the relative differences in specific gravities of the displacer and the mercury, the displacer floats in the mercury, as shown in the normal inoperative position of the relay. At this time there is no contact between the two bodies of mercury 82 and 88, and consequently the circuit between the conductors 28 and 21 is open.

Surrounding the relay is a solenoid coil indicated tically at 88, and disposed beasoaooe tween the metal plates 88 and 81, this coil having a bore through the center through which the tubular portion of the relay 8 extends. Upon energization oi the coil 88 by closing a circuit through the conductors 88 and 88, the coil is energized and the magnetic action results in pulling the displacer 88 downwardly into the body of mercury 88. This displaces the mercury so that it rises in the annular space between the sleeve l2 and the shell until it breaks over the upper edge of the sleeve i2 and flows into contact with the body of mercury 88. completing a circuit between the conductors 88 and 81. So long as the coil is energised, the displacer remains in this position, but upon de-energization of the coil, the spacer moves upwardly due to its smaller specific gravity, consequently lowering the level of the mercury body 88 and breaking contact over the edge of the sleeve l8.

It'will thus be seen that a mercury to mercury making and breaking of contact is effected over the refractory sleeve l8 and that any are which might occur is located within the refractory sleeve 88, thereby preventing any possibility of arcing between the mercury and any adjacent metallic surface. As a result. the metallic surfaces are protected against possible pitting or burning caused by such arcs and a substantially uniform point of making and breaking contact is provided.

It will be noted that the body of mercury 88 has appreciable surface contact with the face of the electrode l8 so as to reduce the contact resistance between the electrode and this body of mercury. Similarly. the body of mercury 88 has considerable surface contact with the tubular shell 8 to insure low contact resistance therebetween, thereby reducing the resistance to flow of current through the switch when the coil 88 is ener ized.

Considering now the form of the invention shown in Figures 2 and 3, the switch 8 shown in these figures is similar to the switch disclosed in detail in Figure l. The coil 88 in this embodiment of the invention is mounted in a substantially U-shaped bracket member 88 which has normally extending flanges 82 at the ends thereof which are adapted to be secured to a supporting surface 88 by means of the screws 88. The clamp 88 is normally made with the two parallel clamping surfaces 88 and 81 extending at a slight angle away from each other so that when placed in position they tend to clamp the coil 88 therebetween. The two legs 88 and 81 of the clamp are split, as indicated at 88, to prevent eddy currents therethrough and to reduce the magnetic reluctance of the circuit.

The plates 88 and 88 are apertured to receive the small diameter portion of the switch 8 which extends therethrough and through the bore of the coil 88. The switch is held in osition by means of a Jbolt 88, preferably formed of spring material, having the vertically extending end 81 engaged in the recess 88 in the cap member 88 and having the shank portion extending through suitable openings in the legs 88 and 81 and secured by means of the nut 88 over the upper plate 88 in tensioned relation to hold the switch firmly in position.

To adapt the construction for use with various lengths of relays, a spacer member 88 is provided which may be formed of wood, porcelain, or any similar insulating material and which has a frusto-conical recess 88 therein seating aboutthe frusto-conical surface formed by the enlarged i-clay, is preferably, made-from straight tubularstock comprising the tubular, blankjll, which a at oneend is provided withia q pte b dradiallywith respectto' the axis of the relay.

tion {defining the,gahoiilderQ66. -receiizing the ceramic refractory envelope 61. 'l'hislrnernber 81 is held-on theshoulder, by means of the ..resili ent, gasket -68 corresponding to, the A gasket I l8compressedshy-m ans;iotth d c "h ld 111 Thus the bolt servesnot only to hold the relay against downward displacement relative tothe coil 05,but also prevents rotation of the relay 5 within the clamp,

This provides a very simple mounting arrangement inwhich'the switch can be accurately held in position both axially and rotatably,7and' in- I -sur'esa quick means of assembling the switch in position relative tothecoil. 1 I 1 Considering "now the embodiment of the invention shown in Figure 4, the relay '65 of this form of the invention is of shorter length than the shell 5 of Figure 1 and is provided with a different type of insert indicated generally at 66 The insert 66 in this form of the invention seats against the frusto-conicalshoulder 61-0f the shell 65, and is provided with the bore I58 which is-of substan'tially'the same diameter as'the diameter of the tubular portion of the shell. Projecting "through the insert 66 is an electrode 69 having the shouldered portion 10. limiting axial movement of this electrode inwardly of the insert. The

gasket I0 corresponding to the gasket of Figure 1 seals the insert and electrode in position, being held in compressed position by the compression member 20 secured in place by the retaining ring 7 23 disposed beneath the spun-over edge 24 of the shell; It will-be noted that theelectrode 69 in this position by thegspun-ovenedge ,OII of-theIIlbe.

Adjacentits lowerend; the blank 66 is provided with la groovedfpcrtion, nywhich produces a shoulder preventing inward movement of the refractory insert 6.3. he insert 03, istsomewhat similar to the insert] censure, v1 ,ll a a: a

vertically extending sleeve portion? 64 ;ofyless length'than the sleeve I! ,or vliflgure. l being providedfwith the bore ,66 opening through the f. flared portion 68,, onto the electrode face of the electrode I 6', this electrode beinggprovided "with the: axially extending shank 11, received within the ceramic compression member 20.; In-

, I terposed between the compression member 20 and the insert 9;! 'isfagasketll corresponding to the gasket clescribedln Figures land 4, which form of the invention projects an appreciable u a distance axially with respect ,to the bore 68 of the insert, and is normally disposed out of contact with respect to the body of mercury I2 carried in the lower end of the shell 65. A suitable two piece dis-placer I3 is provided comprising an inner sleeve of refractor material indicated at H having the annular flange 15 at one end thereof which bears against the internal surface of the tubular portion of the shell 65 and is surrounded by the metallic sleeve of magnetic material indicated at 16 having the annular flange 11 at the end opposite the flange I5, which engages in the .bore 68, whereby the displacer I3 is held against radial movement and is guided by the flanges l5 and II for axial movement within the shell 65.

.Surrounding the lower end of the relay 65 is the coil 18 mounted between the plates 19 and 80, and adapted to be energized through the conductors 82 and 83. Upon energization of this coll, the displacer -I3 is pulled downwardly into the body of mercury 12, thereby causing this mercury to rise until it contacts the electrode 69 completing a circuit between the shell 65 and conductor 26 and the electrode 29 and conductor 21. So long as the coil remains energized, the displace is held in immersed position maintaining this circuit closed, but upon de-energization of the coil, the displacer I3 rises, breaking the circuit between the body of mercury I2 and electrode 69, and consequently opening the-circuit. It will thus be apparent that this switch provides a metal to mercury contact, and is normally in open position, the circuit being closed therethrough upon energization of the solenoid coil.

In Figure 5 I have provided a further modification of the'structure in connection with a normally closed type relay.

In this form of the invention, the shell of the is compressed in positionv to seal this end. of the switchand held in place bythespun-over edge .2 0v of the,blank engaging over theretaining I ring,23. a I

In this f onn.o f;the,-invention ametallic displacer 01 is provided having thebosses or 'lugs 68 forguiding the same-for axial movement within the tube and preventing any possible bindingvthereof hithe tube. The displacer 61 is normally, of suflicient mass so that it-rests-in, the

position shownin Figure 5, whereby .sufl lcient mercury in the mercury body. I 00-is displaced .to run overthe end oi the sleeve 94 and roducecontact with the body of mercury I02 disposed in the, bore 96 of the sleeve.v Thus, this switch provides a construction in which the circuit is normally closed. Upon energization of the coil I03, the displacer 91 is lifted, thereby allowing the outer body of mercury I00 to drop in height until the circuit is broken between the bodies I00 .andallilover the peripheral edge of the sleeve 64.

It will therefore be seen that a mercury to mercury making andbreaking 01' contact is effected in the relay shown in Figure 5, and that any possible arcing which occurs will-occur over the refractory surface of the edge of the sleeve 04. Due to the fact that an annular contact is effected, there is an appreciable cross section of mercury whenevercontact is made in the relay, thereby materially reducing the internal resistance of the relay.

In Figure 6 I: have shown a form of the invention utilizing'the same end closure as described in connection with the upper end of the shell 65,-described in Figure 5, but in which the blank I06 has the enlarged lower end I06-defined by the frusto-conical surface I01. This takes the place of the annular groove 92 of the blank 65 of Figure 5, and forms a shoulder for receiving the refractory insert I08 to limit its axial inward movement. The refractory I06 is also provided with an axially extending cylindrical portion I09 defining a bore I I0 which opens onto the electrode face I5 01' the electrode head I6, this electrode corresponding to that described in connection with Figures 1 and5. The relay of Figure 6 is provided with a displacer 9'! corresponding to the displacer of Figure 5, which functions in the same manner for opening the circuit through the relay upon energization of a envelope for displacing said second body 01' mercury over the upper end of said extension into contact with said confined body of mercury.

7. A relay comprising a tubular metal envelope having an annular shoulder intermediate its ends. a ceramic insert of tubular form having an annular shoulder resting against said first shoulder, the insert having an upper end portion of reduced outside diameter between which and the side walls of the envelope a mercury retaining chamber is formed, a body of mercury in said chamber and a body of mercury in said reduced end portion, a closure for sealing the lower end of the envelope holding said ceramic in place against said shoulder, said closure supporting a central electrode having an external terminal at its outer end and an intermediate terminal in electrical contact with the mercury in the reduced upper end portion, and a tubular displacer surrounding the reduced upper end of the ceramic and being adapted to be operated magnetically.

8. The combination of claim 7 characterized by the internal terminal being of larger diameter than the bore of the upper end of the ceramic insert, and the insert having an enlargement of the bore adjacent said internal terminal to provide an extended area of contact of the mercury in the ceramic insert with said internal terminal.

UNO C. HEDIN. 

